The present invention relates to a blood collection assembly for use with a blood collection container, and more particularly, concerns a blood collection assembly which maintains the blood collection container in fixed position during the blood collecting procedure thereby preventing the container from being pushed outwardly during such procedure.
Many blood collection assemblies are used nowadays for taking multiple blood samples from a patient. Various types of these blood collection assemblies or blood sampling devices are very well known in the art. Generally speaking, these blood collection assemblies include a receptacle or tubular holder into which a blood collection container or tube is received. A needle cannula extends through the receptacle's closed end, the cannula having an external point and an internal point. The external point is for insertion of the cannula into the vein of the patient, whereas the interior point is meant to puncture the penetrable closure which generally stoppers the open end of the blood collection container. Thus, by sliding the collection container into the open end of the collection receptacle, the interior point of the cannula pierces the closure of the container and can thereby deliver blood into the container.
One particular problem which arises in this general type of blood collection assembly concerns the maintenance of the container in a substantially fixed position while inserted in the receptacle. There is a tendency for the container to back off or push out of the receptacle, perhaps due to the penetration forces of the cannula through the penetrable closure of the blood container. With this occurrence, it becomes necessary for the operator of the blood collection assembly to maintain both hands on the entire assembly, one hand holding the receptacle in place in the patient, the other hand holding the blood collection container in position within the receptacle of the collection assembly.
This occurrence of blood collection container push out has become greatly magnified in those instances where the collection assembly includes a spring-resilient valve sheath covering the interior cannula inside the receptacle. This type of valve sheath has become more prevalent especially in the collection assemblies for taking multiple blood samples. The sheath is generally a thin, flexible elastomeric material with self-sealing properties; it covers the interior cannula and thereby prevents blood or other fluids from flowing through the cannula. When the blood collection container is inserted into the receptacle, the leading edge of the closure pushes against the sheath so that the point of the interior cannula pierces the sheath and also penetrates the closure itself. Further inward movement of the blood container then effectively squeezes the sheath, in accordion-like fashion, against the closed end of the receptacle. When the blood collection container is withdrawn, the resiliency of the sheath forces the same to return to its normal relaxed condition, covering the interior cannula and effectively serving as a valve to prevent blood from flowing therethrough. This is most effective for allowing multiple blood sampling, wherein the first blood collection container has to be withdrawn and then another collection container re-inserted into the receptacle. This type of valve sheath is disclosed, for instance, in U.S. Pat. Nos. 3,469,572; 4,136,794; and 4,140,108.
It can be appreciated that every time the blood collection container forces the spring-resilient sheath into its compressed, accordion-like fashion, the sheath serves as a loaded spring. If the operator of the blood collection assembly fails to hold the collection container in a properly seated condition, the compressed sheath has a tendency to urge the collection container outwardly to push the same, perhaps off and away from the interior cannula. This would thereby result in no blood being collected inside the container. Accordingly, this type of blood collection assembly with such a spring-resilient valve sheath, has heretofore demanded that the operator keep both hands on the assembly in order to keep it functioning properly. It can also be appreciated, that when the operator has to push inwardly against the collection container for proper usage, this could cause accidental, deeper penetration of the exterior cannula into the vein of the patient. Thus, this inward pushing against the collection container may give rise to more instances of potential injury to the patient, or else cause traumatic effects to the vein being tapped. With the foregoing in mind, there is a demand for effectively maintaining the blood collection container in proper position in the collection assembly while, at the same time, eliminating the need to constantly exert an inward force against the container. It is to the solution of this problem, which heretofore has been basically unsolved, that the present invention is directed.